March 1, 2010

Cornell Researchers Discover How Fruit Flies Stay on Course

Imagine attaching two magnets on the wings of an airplane which then flies through a magnetic field that distorts the plane’s course. The unfortunate pilots in the plane, struggling for their lives, would have to frantically figure out a sequence of commands to stabilize the plane.

For fruit flies, however, the stabilizing process is much simpler. With just a slight adjustment on their wings, which flap 250 times per second, these tiny creatures could put themselves back on course with ease.

Such is the recent discovery of a University research team, led by Prof. Jane Wang, mechanical and aerospace engineering, Prof. Itai Cohen, physics, and Prof. John Guckenheimer, mathematics.

Wang, who has studied the physics of flight for a decade, explained that two experiments aim to analyze two separate phenomena — how fruit flies cope with a sudden perturbation, and how they make a sharp turn to correct the course.

Advanced technology plays a vital role in the experiments, which detect the smallest movements of the flies’ wings. Thanks to high speed video cameras that can capture 8,000 frames per second, the team was able to detect the minute adjustments made by the rapidly flapping wings, according to Attila Bergou Ph.D. ’09, the first author of the paper “Fruit flies modulate passive wing pitching to generate in-flight turns.”

The three high-tech cameras — each of which cost approximately $35,000 — produced hundreds of films, in which about 10 were analyzed in great detail.

Describing fruit flies as “flying machines with complicated brains,” Wang had first expected that complex movements direct how flies make sharp turns, which could be done in 0.1 seconds. The results, however, surprised her.

“There is a very simple control-mechanism that can explain the turn of an insect,” Wang said, adding that a fast turn can be explained with one single variable.

Although the researchers found it hard to pinpoint how this discovery can be applied to aerospace engineering, both Wang and Bergou said aircraft designers and engineers can learn much from these insects. While rigid airplanes have difficulty stabilizing itself through a turbulence, animals are soft and respond to their environment with much flexibility, according to Bergou.

“They take advantage of and respond to airflow and inertia [to control wing movements,]” said Bergou, who is now a post-doctoral researcher and studies bats at Brown University.

Prof. Itai Cohen, physics, Prof. John Guckenheimer, mathematics, and Leif Ristroph grad are the co-authors of the research. The four-paged paper is submitted to the journal Physical Review Letters and is currently under review. The team also produced a paper entitled “Discovering the flight auto-stabilizer of fruit flies by inducing aerial stumbles,” which was published online yesterday in Proceedings of the National Academy of Sciences.